Značaj polimorfizama u genima za glukokortikoidni i adrenokortikotropni receptor u nastanku adrenalnih incidentaloma

Abstract

UVOD: Glukokortikoidni hormoni (GC) ostvaruju svoje efekte vezivanjem za glukokortikoidni receptor (GR). Adrenokortikotropni hormon (ACTH) reguliše sintezu GC vezivanjem za ACTH receptor (ACTHR). Prisustvo polimorfizama u genu za GR (BclI, N363S, ER22/23EK and A3669G) i promotoru ACTHR može uticati na efekte glukokortikoida i predispoziciju za nastanak unilateralnih adrenalnih incidentaloma. CILJ RADA: Utvrđivanje mogućeg uticaja funkcionalnih polimorfizama u genima za GR i ACTHR na predispoziciju za nastanak adrenalnih incidentaloma i osetljivost na GC i ispitivanje ekspresije GR u tumorskom, peritumorskom i zdravom adrenokortikalnom tkivu. METODE: U ispitivanje je bilo uključeno 112 pacijenata i 100 zdravih dobrovoljaca, koji su podvrgnuti metaboličkom, genetičkom, biohemijskom i antropometrijskom testiranju. DNK je dobijena iz leukocita periferne krvi. Prisustvo polimorfizama je detektovano metodama PCR, RFLP i sekvenciranja DNK. Uzorci tkiva su analizirani imunohistohemijskom metodom. REZULTATI: Prisustvo dužeg C alela BclI (p<0.001) polimorfizma i kraćeg G alela A3669G (p<0.001) polimorfizma GR gena su bili nezavisni prediktori adrenalnih incidentaloma. Pacijenti sa prisutnim C alelom BclI su imali veće tumore (p=0.002), a oni sa G alelom A3669G više vrednosti postdeksametazonskog kortizola (p=0.025). Istovremeno prisustvo oba alela je koreliralo sa manjim obimom struka (p=0.002), a višim baznim i postdeksametazonskog kortizolom (p=0.024). Smanjena ekspresija GRα i GRβ izoformi zapažena je u tumorskom, a GRα u peritumorskom tkivu. Lokalizacija GRβ je bila dominantno nukleusna. ZAKLJUČAK: Prisustvo C alela BclI i G alela A3669G polimorfizmama gena za GR se nalaze u vezi sa nastankom unilateralnih adrenalnim incidentalomima, a njihovo zajedničko prisustvo dovodi do smanjene osetljivosti na GC. Stečena intraadenomatozna glukokortikoidna rezistencija može da dovede do disregulacije produkcije kortizola i rasta tumora u isto vreme, dok prirodna osetljivost na glukokortikoide najverovatnije modifikuje ove efekte.

INTRODUCTION: Glucocorticoid hormones (GCs) accomplish their effects through binding to glucocorticoid receptor (GR). Adrenocorticotropic hormone (ACTH) regulates synthesis of GCs through binding to ACTH receptor (ACTHR). Presence of common GR gene (BclI, N363S, ER22/23EK and A3669G) and ACTHR promoter polymorphisms can modulate GCs sensitivity. OBJECTIVE: The aim of present study was to determine weather functional polymorphisms in GR and ACTHR genes influence susceptibility for unilateral adrenal incidentalomas and GC sensitivity, and to investigate GR expression in tumorous, peritumorous and normal adrenocortical tissue samples. METHODS: The study included 112 patients with adrenal incidentalomas and 100 population-matched controls. All subjects underwent metabolic, genetic, biochemical and anthropometric testing. DNA was obtained from peripheral blood leucocytes. The polymorphisms were detected using PCR, RFLP and DNA sequencing. Tissue samples were studied by immunohistochemistry. RESULTS: GR gene variant, C allele of BclI (p<0.001) and G allele of A3669G (p<0.001) polymorphisms were independent predictors of adrenal incidentalomas. Patients with present C allele had larger tumors (p=0.002), but those with G allele had higher postdexamethasone serum cortisol (p=0.025). Both allele carriers had lesser waist circumference (p=0.002), higher basal (p=0.024) and postdexamethasone cortisol concentrations. In tumorous tissues GRα and GRβ isoforms had lower expression, but only GRα in peritumorous tissue. Localization of GRβ was dominantly nuclear. CONCLUSION: GR gene variants, larger C allele of BclI and minor 3669G allele are associated with adrenal incidentalomas. Their concurrent presence in patients reduces GC sensitivity. The acquired tumorous GC resistance probably promote dysregulated cortisol production and tumor growth, but natural sensitivity to glucocorticoides maybe modifies these effects.